Merge pull request #1005 from touilleMan/master

Raise error if save_condition fails #991

AUTHORS

@@ -223,3 +223,4 @@ that much better:
  * Kiryl Yermakou (https://github.com/rma4ok)
  * Matthieu Rigal (https://github.com/MRigal)
  * Charanpal Dhanjal (https://github.com/charanpald)
+ * Emmanuel Leblond (https://github.com/touilleMan)

docs/changelog.rst

@@ -20,6 +20,7 @@ Changes in 0.9.X - DEV
 - Support for PyMongo 3+ #946
 - Fix for issue where FileField deletion did not free space in GridFS. 
 - No_dereference() not respected on embedded docs containing reference. #517
+- Document save raise an exception if save_condition fails #1005
 
 Changes in 0.9.0
 ================

mongoengine/document.py

@@ -266,7 +266,8 @@ class Document(BaseDocument):
             to cascading saves.  Implies ``cascade=True``.
         :param _refs: A list of processed references used in cascading saves
         :param save_condition: only perform save if matching record in db
-            satisfies condition(s) (e.g., version number)
+            satisfies condition(s) (e.g. version number).
+            Raises :class:`OperationError` if the conditions are not satisfied
 
         .. versionchanged:: 0.5
             In existing documents it only saves changed fields using
@@ -284,6 +285,8 @@ class Document(BaseDocument):
         .. versionchanged:: 0.8.5
             Optional save_condition that only overwrites existing documents
             if the condition is satisfied in the current db record.
+        .. versionchanged:: 0.10
+            :class:`OperationError` exception raised if save_condition fails.
         """
         signals.pre_save.send(self.__class__, document=self)
 
@@ -348,6 +351,9 @@ class Document(BaseDocument):
                     upsert = save_condition is None
                     last_error = collection.update(select_dict, update_query,
                                                    upsert=upsert, **write_concern)
+                    if not upsert and last_error['nModified'] == 0:
+                        raise OperationError('Race condition preventing'
+                                             ' document update detected')
                     created = is_new_object(last_error)
 
             if cascade is None:

tests/document/instance.py

@@ -954,11 +954,12 @@ class InstanceTest(unittest.TestCase):
         self.assertEqual(w1.save_id, UUID(1))
         self.assertEqual(w1.count, 0)
 
-        # mismatch in save_condition prevents save
+        # mismatch in save_condition prevents save and raise exception
         flip(w1)
         self.assertTrue(w1.toggle)
         self.assertEqual(w1.count, 1)
-        w1.save(save_condition={'save_id': UUID(42)})
+        self.assertRaises(OperationError,
+            w1.save, save_condition={'save_id': UUID(42)})
         w1.reload()
         self.assertFalse(w1.toggle)
         self.assertEqual(w1.count, 0)
@@ -986,7 +987,8 @@ class InstanceTest(unittest.TestCase):
         self.assertEqual(w1.count, 2)
         flip(w2)
         flip(w2)
-        w2.save(save_condition={'save_id': old_id})
+        self.assertRaises(OperationError,
+            w2.save, save_condition={'save_id': old_id})
         w2.reload()
         self.assertFalse(w2.toggle)
         self.assertEqual(w2.count, 2)
@@ -998,7 +1000,8 @@ class InstanceTest(unittest.TestCase):
         self.assertTrue(w1.toggle)
         self.assertEqual(w1.count, 3)
         flip(w1)
-        w1.save(save_condition={'count__gte': w1.count})
+        self.assertRaises(OperationError,
+            w1.save, save_condition={'count__gte': w1.count})
         w1.reload()
         self.assertTrue(w1.toggle)
         self.assertEqual(w1.count, 3)